My 1989 dually has an erratic idle problem. I took apart the TBI unit along with the poweraid block. Cleaned them both with fuel injector cleaner and put back together. If I tap the accelerator it idles high until I "tap" The spring lever on the TBI unit itself and then the idle goes down to normal. I have tried using wd40 but the problem remains. I thought butterflies just open and close and thats it? I just replaced today the TPS and is still doing the same.
Could the butterflies be wore-out? Has anybody have this problem before? What it the solution?